add @navbar-collapse-max-height Less variable
reorder sections of About docs page

most folks are probably more interested in History and Team than Branding
Merge pull request #12327 from twbs/about-ordering

reorder sections of About docs page
Merge pull request #12326 from twbs/navbar-var

add @navbar-collapse-max-height Less variable
Reorder nav of About docs page
Reorder lead info of About docs page
Merge pull request #12334 from Quy/master

Reorder lead/nav of About docs page